A system-on-a-chip (SoC) is an integrated design of hardware and software components that are combined to form a computer on a single integrated circuit. One of the benefits of implementing a SoC is the ability to integrate various types of functionality onto a single chip, rather than interconnecting multiple chips that implement independent functions. For example, a SoC may be used within a mobile telephone to integrate digital, analog, and radio frequency functions on a single chip. This type of integration can save significant space and allow devices to be made smaller and more powerful.
Within a SoC, different hardware and software components (also referred to as IP blocks and modules) are combined to implement specific functionality. One complication with designing a SoC is that some of the components may be designed to operate at different power requirements, including different voltages and/or different operating frequencies. Additionally, it may be useful in some situations to be able to independently control different groups of components, for example, to place certain components in a sleep mode when full functionality of the components is not required.
Given the prospect of consuming a lot of power by operating all of the components within a SoC, many SoC designers are concerned about power efficient technologies. One power management design approach combines components with similar power requirements into groups, which are referred to as power islands or, in some instances, voltage islands. All of the components within a power island typically have similar power characteristics that are unique from the power characteristics of other power islands. Using power islands, the components within each group may be independently switched on or off. By turning off power to a power island during a time that the power island is not required for operation of a device, the total power consumption of the device can be reduced. Then, when the components of that power island are needed again, the power for that power island can be turned on again. In this way, the battery life of a portable electronic device may be significantly increased by suppressing leakage current of components that are temporarily unused.
While conventional SoC implementations that use power islands to implement dynamic voltage and frequency scaling (DVFS) can save a substantial amount of power, there are still limitations on the amount of power that can be saved using conventional power island designs. In particular, some memory components on an island do not scale to the same degree as logic components and, hence, the memory components of the power island can limit the range that the logic can be scaled. More specifically, internal memory typically has a very narrow voltage range, while logic components typically have a wider voltage range. Hence, the narrow voltage range of the memory limits the voltage range that can be applied to the logic components in the same power island. Accordingly, the memory components which limit the amount of logic scaling also limit the ability to save power through DVFS.
In contrast to embodiments which limit the voltage range of the logic to match the voltage range of the memory, some conventional embodiments may use memory designed for a wider range of voltages. However, designing memory for a wider voltage range prevents optimal memory design and generally results in memory with inferior power and/or speed performance. Also, memory that is designed for a wider voltage range generally uses larger memory cells, which increases the size of the power island.